Deflecting circuits



Sept 14, 1948.- v .1.. R. KlRKwooD ET Al. 2,449,169

DEFLECTING CIRCUITS Filed June 4, 1946 BLANK/NG PULSES o wl! g DU @j N INVENTOR. LanezzR.K11-]wo0d& gi/@HIE GLHOIST Patented Sept. 1.4, 1948 Holst, Mount Healthy, Ohio, .assignors itc Radio Corporation of America, a .corporation offDelaf- Wale Application .lune 2i, 1946, Serial No. 674,184

,1l Claims.

z-Our invention `relates to-cathode-ray deflecting .circuits and particularly to the production of de- -.-flecting Waves Whichfhave a fast return line por- .tion .and which VAhave a useful delecting fportion Ethatfis shaped toproduce a-cathode-ray trace in .which the start of the trace is expanded, 'thereby increasing theiaccuracy with which observations may be made during this time interval. rThe .present-invention is-an improvement over the de- -fecting circuit described 'and claimed in copending application Serial .'No. 583,255, filed March 17, 1945, inthe namezof'GeorgefD. Hulst, Jr., and entitled Cathode ray deflection circuit.

fCircuits-oi ithe above-lmentioned `type are particularly-useful in .aircraft or ship radio navigationsystema lsuch as the -Loran system, `in which radio pulses are received from two ground transllmitters andare made to appear on apair of cath- `.ode ray vtraces where the two pulses are brought into ,alignment .or coincidence. Our copending .application-SerialNo,682,50G, iiled July 10, 1946, f now vPatent .'Nmnber .2,442,692 and entitled VRadio 4navigation system,.shows lout does not claim the .present invention.

Anlob'ject of the zpresent invention is to pro- -vide an improved method-of and means for 'producing a fast-sweep deflecting wave.

-Another object :of ethe invention is tofprovide aan improved circuit for producing a deecting wave having useful deecting :portions Vof differ- .entslopes r-Still another yobject of theinvention isto proyvide yan improved Icircuit for A.producing ,a `de- .iiecting Wave having areturn-line :portion that returns rapidly to a predetermined -voltage level.

yStillanother'object ofthe invention is to .pro- =videfa `substantially square wave-time to coincide with the startand't'heendof thefast-sweep wave .for ruseas a -blanking or 'unhlanking signal.

lnraccor'dance with the present invention there is -a `wave shaping network lthat comprises .two

...network sections having different discharging time .-constants. During -the return-line or retraceperiod the network Ysections are 'charged rapidly to full voltage through separate'vacuum v tubes. vThe usefuldeiiection Wave'portions of-difriferentfslopes are iproducedfasthe network sections discharge.

v'Ihefinvention -will be rbetter understoodfrom lthe following descrptiontakenin connectionwith the accompanying-drawing in which liigurel is a circuit diagramoffan:embodiment of theinvention together with the principal :Wave shapes,

vvFigure `2 is ragroup of .graphsthatfare referred toin explaining the invention, and

Figure '3 lis -an enlarged l.graph =of some of the pulsessho-wn Yin Figure 1.

`Referring to Fig, 1.0i the drawing, :the circuit fcomprisesiavacuum tube lll-andra shaping net- A grids i are driven Vbeyond the cut-ofi value during fa large portion (indicated by stipplingv--in =Fig.:=2)

..2 work Athat `comprises itwo sections .consisting .of vcathoderesistors :H Iand l2 shunted -by capacitors E13 and ifi, respectively, identified-as network sections t6 and FL The shaping .network-lturther comprises a delay line section-I t-comprisingseries .resistors i9 andfshunt capacitors 2l connected across'the network section l and terminatedlin a'resistor 22and in the network section I1. The fast-sweep wave 1F (Fig. 2) 4is :taken oi the resistor ft2 through an adjustable tap 23, the set --E immediately yfollowing `the discharging Aportion f-g is :steeper with the ypreserx-t..i1nproved ,circuit than with -the -circuit .of the above-.mentioned Hulst application. Thus, thedeecting circuit network Vis brought to theiull charge voltagelevel .e1 in such a .short time that itis alwayscharged to the level .e1 before .a deflecting wave portion such as f-g occurs even-if thesuccessive deflecting wave .portionsare separated .by only short time intervals.

The vacuum .tubeQZS vhas its cathode connected .tothe .junction point .of :the resistors .H .andlZ so that the capacitor lli of network l1 may .be charged Athrough .the .tubeZB. The anodepf the Vtulce .25 lis connected directly to the +B voltage. 'Ihegridsof `the .tubes-10 l and ..26 areconnected .to points on a potentiometer .resistor -21 .with .the

. .gr'dof the tubef2`6 connected toa point of slightly .Waves of .different vamplitudes appearing ontlie gridsmof 'tubes Il) and 26 .are indicatedjinfEig..2

as Waves J' and J, respectively. 4It maybenoted that .in the absence of .the 4pulses J .the .grids of the tubes lland 26 are less .positive .withjrespect to ground .than .their .cathodes; however, .the resulting Vbias .is 'less ythan vthat required vto bias v'the ...tubes to plate current cut-off.

In operation r-the ltube '.26 .in conjunction with r.the,network.I'l .produces ithe lesser slope -.0f the slope Iof 4the r`wave fportion f--g for the expanded sportionof4 the sweep. When Ythe Inegative pulses .dare applied' to the grids-.of tuloesl landi25,1.both

of the pulseduration. During the periodoicut- --olythetubes IB andfzl drawnnocurrentfandthe across the two networks IG and II.

resistor I2 of lthis network at a rate determined by the time constant of resistor I2 and capacitor I4. This time constant is long compared to the out-off interval, and the discharge cycle is interrupted before completion, when the grid of tube 26 returns to its steady state potential, at a value above the cut-off point. rlhe capacitor o network I'I is then recharged through the tube 26 at a much faster rate, determined primarily by the internal resistance of this tube. The voltage wave appearing acrpss the network II is shown at B.

The grid of tube I receives the pulses J' which diler from the pulses applied to the tube 26 only by their greater amplitude. 'Ihe tube IU also normally draws plate current sufficient to develop a cathode bias through the two resistors of networks Il and I2 and to charge the capacitor of network I to a fixed fraction of the steady state cathode potential. When the negative pulses J are applied to the grid of tube I0, the tube Ill is cut oi during the part of the pulse duration as indicated by stippling in Fig. 2. During the cut-off period, the capacitor of network I6 discharges through the resistor of this network at a rate determined by the time constant of the capacitor and resistor. As this timeconstant is short compared to the cut-olf period, complete discharge occurs in the early part of this period. No further action occurs until the grid of tube I0 returns to a value above the cut-off point and the tube I0 again draws current. When tube iii draws current, the capacitor of network I3 is recharged through the tube I Il and its plate resistor I5 to its original potential. The resulting voltage thus developed across the capacitor-resistor network IE provides the steep portion of the wave f--g. The voltage wave appearing across the network I6 is shown at D.

kSince the capacitor of network I6 discharges during the cut-off period, lowering the cathode potential of tube'ZS to a potential equalling that across the capacitor of network I'l, which is also varying, the voltage developed at the cathode of the tube Ill is the sum of the voltages appearing This voltage wave, indicated at E, consists of a steeply sloping leading edge, developed by the rapid discharge of the capacitor of network IE and an abrupt change to a moregradual slope, developed by the discharge or the capacitor of network II. As the recharge period for both cajpacitors lof networks IG and I'I begins at approximately the same time, a steeply sloping return swing is imparted to thecombined wave as desired.

in cut-oir` value is different for the two tubes,

the greater change occurring in tube I0. By applying alarger negative grid pulse to the tube I0 than to the tube 26, this effect is balanced so that the cut-01T period for both tubes ends at nearly the same time; but tubeA ID is always slightly ahead of tube 26, thus placing tube Ill' in control of the length of 'the sweep.

As used in the navigation system of our above- Hmentioned copending application, the start of the fast sweep should be delayed slightly with respect to the starting edges of the controlling pulses J. Two resistor-capacitor sections comprising the network I8 provide the means which produces this delay. This network has a frequency response less than that required to pass the high frequency components developed by the abrupt start of the fast-sweep wave. As a result, the wave F which does pass is modified by the network, starts gradually, producing the desired time delay at the start of the steep portion of the wave front. Except for incidental rounding of the other sharp corners, the remainder of the pulse shape is unaffected and is the same as the wave E.

The portion of the circuit for producing Vthe wave J will now be described. It may comprise an Eccles-Jordan oscillator 3l for producing a square wave M which is supplied over a conductor 32 through a dilerentiating network comprising a capacitor 34 and a resistor 36 to the input circuit of a vacuum tube 33 to produce the wave I.

The wave M is also supplied over a conductor 3'! to suitable delay circuits 38 for producing a wave G in which the timing of the back edge may be manually controlled by means of a knob 39, for example. The delay means 38 may cornprise one or more multivibrators; it preferably comprises two multivibrators in cascade, one providing a coarse delay and the other providing a iine delay.

The wave G is supplied over a conductor 4I to the input circuit of a vacuum tube 42 through a. diiierentiating network comprising a capacitor lli and a resistor 46 to produce the wave I-I. The tubes 33 and 42 have a common plate resistor 43 whereby the input waves of these tubes are combined. The combined waves I and H are widened somewhat by a shunting capacitor 45 and are then clipped by a clipper tube 41 to produce the wave J which comprises successive pairs of pulses, the second pulse of the pair being adjustable in timing. As indicated in Fig. 3, the clipper tube 41 removes the logarithmic tail from the pulses due to the discharge characterstic of capacitor 45 and thus produces the sharp triangular pulses J. As a result, a shorter time interval between successive pulses J is permissible than would otherwise be the case. It will also be noted that the clipping removes the negative pulses present in the waves H and I. The differential mixer tubes 33 and 42 are operated such that the grids are driven more p ositive than the plates whereby the pulses J in the plate circuit are of equal amplitude even though the input pulses I and H may vary slightly in amplitude. Since the width of the pulses J is controlled by the R-C network in the plate circuit (the network comprising capacitor 45 and the associated circuit) and by the clipper setting, their width is independent of such slight variations in the width of the input pulses I and H as may occur. yThe resulting uniformity of the pulses J insures a corresponding uniformity and stability of the deflecting wave F.

The present invention makes it possible to make the second pulse vof a pair of pulses in the wave J occur very shortly after the iirst pulse of the pair and still obtain successive fast sweep cleecting waves f-g of the deecting wave E that always return to the-preset voltage level e1.

Rectangular pulses coincident with vthe sweep Wave E to be used for blanking or unblanking a cathode ray tube, for example, may be taken off assenso +B voltage when thetube l- -isdriven to=cut-of.

We claim `as Your invention:

1. cathode-ray ldeflection :wave .circuit comprising avacuumtube having ananodaafcathode and a control grid, a plurality :of resistor-capacitor circuits having dierent time constants .and connected 'in `:series with :each other, vsaid series connected icircuits being connected in 'series with ztli'e 'catho de-anode .impedance of .said :tube,.means 4:For supplying .direct current to .said circuits rcurrent interruption to a zutilization circuit.

12..;A .cathode ray `deiiecting circuit comprising two Aresistors yconnected in series and .two capac- -itorstconnectedacross'said two resistors, respec- -tively, to vform two wave yshaping networks, a `vacuum 'tubehaving .a cathode, a grid and an l:a-nc'de, said Aresistors: being .connected in series 4relation between said .cathode .and ground, a sec- -ond vacuum tube .having a cathode, agrid and anfanode, the cathode oi:said.second tube being :connected to Y.the -junction .point of said resistors, @meansfor supplying -anodevoltage to said rst tube fthroughfan anode resistor, means for sup- `plying.anodelvoltage directlyto the anode of said second '-tube, -and means .for applying .similar negative pulsesto thegrids of. said tubes with sufficient amplitude to Ydrive .said .tubes beyond anode-current cut-on whereby said .networks are charged lthrough said tubes Ifat the end .of yeach applied pulse and whereby said networks discharge while saidtubesare cut oli to produce a usefu1-deilecting-Wavelwliich appears across said two resistors yin series.

3. The invention according to claim 2 wherein .thewave shaping 'network located between said junction point and ground has ,a longer discharging time .constant than the other of said wave shaping networks.

4. `The invention accordingito claim 2 wherein :.meansiis provided for taking blanking pulses oi .vsaid anode resistor .of Y.the first tube.

35. A cathode-.raydeectionfwave circuitcom- -pri`sing -a pluralityof vacuum tubes each .having an anode, a cathode and a control grid, a plurality of resistor-capacitor circuits having different time constants and connected in series with each other, said series connected circuits being connected in series with the cathode-anode impedance of one of said tubes, means for charging the capacitors of said circuits to a predetermined direct-current potential including means for charging at least one of said capacitors through the cathode-anode impedance of said one tube and means for charging the rest of said capacitors through the anode-cathode impedance or impedances of the remaining tube or tubes of said plurality of tubes, and means for interrupting periodically the flow of charging current through said plurality of tubes to said capacitors including means for applying to the grids of said tubes periodically recurring negative pulses of suicient amplitude -todrive said ftubes periodicalllyto anode current cut-off, Aand means der :applying thesum o'f the voltages that appear across said circuits 'to =a utilization circuit.

e'. A-ca'tho'de-ray deection Wave `circuit comprising two vacuum tubesieach having .an anode, a :cathode .and acontrol grid, -two resistor-acapacitor circuits vhaving different 4time nconstants land v'connected in series with each other, said Vseries connectedfci-rcuits'being connected in series with the Acathode-anode impedance kof done `of said ftlibes, lmeans fior charging the capacitor of ione ci :said circuits to ,a `predetermined yvoltage through the cathode-.anode impedance of fone of Asaid tubes, means :for charging the capacitor of `the :other of said :circuits Sto la predetermined Avoltage :through the .ano de-cathode impedance :of the .other Voi" said tubes, `means for applying -to said grids periodically recurring negative pulses A.or suiiicientamplitudetodrive said tubes periodically to fanode A`current cut-ori, and means for applyingthevoltagethatappears across saidy cirv'cuits -to `a utilization circuit.

7. A-cathode-raydeiiection wave circuit comprisinga plurality oi Vacuum tubes `each having an.anode, a cathode and afcontrol grid, a .plu- -lrality .of resistor-capacitor circuits fhaving lvdiiierent time constants and connected inseriesin the-cathode circuit-of one of said tubes,'oneof1said resist-or-capacitor circuits being .connected 4also in the cathode circuit of another of said tubes, leach resistor-capacitor circuit comprising .a vcapacitor lshunted by 'da lresistor, Ameans "including said Vacuum-tubes for' charging the. capacitors -in 1the respective-cathode circuits of said tubesitora predetermined directcurrent voltage through-,the respective :cathode-anode impedances of Lsaid tubes, andimeans for applying to vsaid grids fperriodically recurring .negative vpulses of sufficient amplitudev .to drive said .rtubes periodically to Aanode current lcut-orf whereby vsaid Vcapacitors :discharge Vthrough their shunting resistors 'during rsaidcut-'o'ii periodspand means for applyingithe vsum-"of 'the lvoltages 'that appear across. said cirv:cuits to =a1utilization circuit.

8. fArcathode-ray deiiection :wave circuit com- Lprsing: a vacuum :tube having an l anode, sal cath- 'o'de .and vafcontrol grid, ya plurality of resistorcapacitor circuits having difterent time lccn- Astantsfand-connected in series with each other, saidseriesconnected circuits being connected i-n yseries with:the-cathode-anodeimpedance of said 'tube,-meansrfor supplying direct-current to Vsaid -circuits through said tube for charging theraipacitorsof saidcircuits to apredetermined'di- -rectscurrent potential, means for `interrupting Iperiodically lthei flow of charging currentsthrough said tube to said circuits, and means for applying the sum of the voltages that appear across said circuits during said periods of current interruption to a utilization circuit, said means for interrupting periodically the flow of charging current comprising means for producing a first group of periodically recurring pulses, means for producing a second group lof periodically recurring pulses that are displaced in phase with respect to said nrst group, a pair of vacuum tubes having input electrodes to which said first and second groups of pulses are applied, respectively, said pair of tubes having a common output resistor whereby said rst and second group of pulses are combined, means for clipping said combined pulses to produce triangular pulses and means for applying them to the control grid of the first-mentioned vacuum tube.

9. A cathode-'ray deection wave circuit comprising a vacuum tube having an anode, a cathode and a control grid, a plurality of resistorcapacitor circuits having diierent time constants and connected in series with each other, said series connected circuits being connected in series with the cathode-anode impedance of said tube, means for supplying direct current to-said circuits through said tube for charging thecapactors of said circuits to a predetermineddirectcurrent potential, means for interrupting periodically the flow of charging current through said tube to said circuits, and means for applying the sum of the Ivoltages thatappear across said circuits during said periods of current interruption to a utilization circuit, said means for interrupting periodically the flow of charging current comprising means for producing a first group of periodically recurring pulses, fmeans for producing a second group of periodically recurring pulses that are displaced in phase with respect to said rst group, a pair of vacuum tubes having input electrodes to which said rst and second groups of pulses are applied, respectively, said pair of tubes having a common output resistor whereby said rst and second group of pulses are combined, a direct-current connection from said output resistor to the control grid of the first-mentioned vacuum tube, and a Vclipping diode connected between said direct-current connection and ground.

10. A cathode-ray deflection wave circuit comprising Ya vacuum tube having an anode, a cathode and a control grid, a plurality of resistorcapacitor circuits having different time constants and connected in series with each other,vsaid rseries connected circuits being connected in series with the cathode-anode impedance of said tube, means for supplying direct current to said circuits through said tube for charging the capacitors of said circuits to a predetermined direct-current potential, means for interrupting periodically the ow of charging current through rsaid tube to said circuits, and means for apply- `to said rst group,` a pair of vacuum'tubeshaving input electrodes to which said firs-t and second groupsrof pulses are applied, respectively, 5

saidpair of tubes having a common output resistor whereby said first and second group of pulses are combined, a direct-current connection from said output resistor to the control grid of `the rst-mentioned vacuum tube, a capacitor connected between said direct-current connection and ground to widen said pulses, and a clipping diode connected between said direct-current connection and ground.

11. A cathode-ray deection wave circuit comprising a vacuum tube having an anode, a cathode and a control grid, a plurality of resistorcapacitor circuits having diierent time constants and connected in series `with each other, said series connected circuits `being connected in series Iwith the cathode-anode impedance of said tube, means for supplying direct current to said circuits through said tube for charging the capacitors of said circuits to a predetermined direct-,current potential, a second vacuum tube having an anode, a cathode and a control grid, the cathode of `said second tube `being connected to a junction point of said series connected resistorcapacitor circuits whereby a portion of said circuits may be charged through said second tube, means for interrupting periodically the ow of charging current through said tubes to said circuits, and means `for applying the sum of the voltages that appear across said circuits during said periods of current interruption to a utilization circuit, said means for interrupting periodically the ow of charging currentcomprising means for producing a rstgroup of periodically recurring pulses, means for producing a second group of periodically recurring pulses that are displaced in phase with respect to said rst group, a pair of vacuum tubes havinginput electrodes to which said first and secondvgroups of pulses are applied, respectively, said pair of tubes having a common output resistor whereby said first and d. il

second group of pulses are combined, ardirectcurrent connection from said output resistorto thecontrol grids of the rst and second vacuum tubes, and a clipping diode connected between said direct-current connection and ground.

LOREN R. KIRKWOOD. PAUL F. G. HOLST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name vDate 2,222,426 White Nov. 19, 1940 2,282,104 Tuniek May 5, 1942 2,282,105 Tuniek May 5, 1942 2,366,307 Anderson Jan, 2, 1945 

